1. Field of the Invention
The present invention relates to a technique for processing image data of moving images.
2. Description of Related Art
For example, a system, in which position information of a moving object changing every second is dynamically obtained from data of a GPS (Global Positioning System) and the results are obtained, is in practical use. However, in this technique, data from a GPS satellite may not be always obtained with high accuracy. In particular, this problem may occur in movement in urban areas in which high buildings are built, movement in tunnels, movement in mountainous areas and forest areas, and movement in bad weather. Due to this, when position detection accuracy is required on the order of meter or less, in position detecting techniques depending on only the GPS, the accuracy is insufficient. In this case, when data is obtained in environments in which information cannot be obtained from a GPS or accuracy of information from a GPS is deteriorated, a method is necessary in which position information changing every second is obtained in any way with high accuracy. A technique has been known in which detection of position changing every second is performed based on image sequences by using principle of photographic measurement (see Japanese Unexamined Patent Application Publication No. 2007-171048). In this technique, when information from a UPS is interrupted, a position of a camera changing dynamically can be sequentially obtained from analysis of image sequences by calculation.
However, in the method in which a position of a camera or an object to be measured is obtained from image sequences, errors may be generated. That is, in the method in which a position of a camera or an object to be measured is calculated, processing is executed such that matching relationship between feature points of the object to be measured, which are obtained from (n)th frame image, and feature points of the object to be measured, which are obtained from (n+1)th frame image, is calculated, and feature points of the object to be measured is tracked every second in accordance with change in a photographing position. In this processing, errors of track accuracy of the feature points of the object to be measured, which are successive between frame images next to each other on a time axis, are gradually accumulated.
For example, a technique for overcoming this problem has been proposed in Journal of Information Processing Society of Japan Vol. 47, No. SIG 5 (CVIM 13), Hirotsugu Yokoji, pages 69 to 79, Japanese Unexamined Patent Application Publication No. 2006-250917, and Japanese Unexamined Patent Application Publication No. 2010-14443. The invention described in Journal of Information Processing Society of Japan Vol. 47, No. SIG 5 (CVIM 13), Hirotsugu Yokoji, pages 69 to 79, is directed to a method which simultaneously minimizes an error (reprojection error) between coordinates, in which an estimated three-dimensional position is projected on the image, and coordinates detected on the image, and a position error defined by GPS positioned values. The invention described in Japanese Unexamined Patent Application Publication No. 2006-250917 is directed to a method in which camera vector (CV) data showing the position of the camera and three-dimensional rotational position of the object based on video images, and position measured data of a moving object, are synchronized in time by reference time and are compared on the same time axis, and they are complementarily corrected. The invention described in Japanese Unexamined Patent Application Publication No. 2010-14443 is directed to a method in which processing is repeated in which calculated exterior orientation parameters are corrected based on difference between photographing timing of images and obtaining timing of at least one of a photographing position and a photographing attitude provided from an external section, so that errors are reduced.